In order to increase the number of users that can simultaneously use a cell's resources (e.g., spectrum), as well as reducing inter-cell interference by shrinking footprint of downlink signals, Active Antenna Array solutions (AAS) may be used to split cells into sectors; such cell splitting may be done in both Azimuth and Elevation domains, breaking up the cell into horizontal or vertical beams, or 2D (two dimensional) beams. Efficient reuse of spectrum in such sectors apparatus requires knowledge of “cross-talk” between different beams as seen by the UEs. It is also desirable to shape the beams in such a way that will minimize such cross-talk; internal cross-talk created by side-lobes and grating lobes should be controlled by antenna technology means, while external cross-talk sources coming from environmental reflections (multipath) should be handled by informed antennas weight setting.
As typical AAS solutions require multiplication of transceivers and baseband circuitries, sometimes driving costs up, architectures that may implement MU (multiple users) MIMO base station with less hardware may be advantageous in cases where cost sensitivity is significant.